A Look At The Science Of 'Avatar'

This past holiday season's movie blockbuster Avatar was great for getting the public thinking about the possibility of extraterrestrial life.

When discussing the movie on the drive home from the cinema, folks must wonder if there could be such a paradise moon as Pandora where the blue skinned Na'vi aliens live.

WATCH: Avatar, The Science Behind The Movie. Including exclusive interviews with director James Cameron, cast and crew, plus a behind the scenes look at how Pandora was created.

When the first installment of Star Wars hit the screen in 1977 with its rich tapestry of alien worlds, astronomers didn't even know if planets orbited other stars. I remember musing about the rebel base being located on a jungle moon orbiting the gas giant planet Yavin. Could such moons exist? At the time I thought it was very unlikely. The moons in our solar system all looked lifeless.

Since 1977 we've discovered over 400 planets orbiting others stars. We've reconnoitered the solar system. Based on today's knowledge, what about Avatar is scientifically plausible or implausible? (I won't say impossible because science fiction author Arthur C. Clarke once admonished that you'll almost always wind up being wrong if you say something is impossible). Also, any sci-fi story needs artistic license, so I won't even pick on ideas of faster-than light travel and English-speaking altruistic aliens.

Here's a quick look at some of the science in Avatar:

Living Moons – Inhabitable moons are probably the most common place to find life in the Milky Way, simply because large moons outnumber planets by at least a factor of 10, if our solar system is a typical example. This was nicely described in a previous blog by my colleague Ian O'Neill.

Saturn's giant moon Titan (shown above) could be the archetype of inhabitable moons. It is as geologically and meteorologically diverse as Earth. My planetary scientist friends nickname it "Earth II."

The only problem is that Titan is 1 billion miles from the sun, and therefore a chilly -300 degrees Fahrenheit. But warm it up and Titan would have the potential to be a living world because it is knee deep in organic compounds. This will happen in about 5 billion years when the habitable zone around our aging red giant sun sweeps out to Saturn's distance.

Alien Biology – The biosphere of Pandora supports an extraterrestrial Serengeti of diverse creatures. Biological evolution certainly took a different road on Pandora, as expected. The respiratory systems of many of the species appear to operate differently from ours. Bioluminescence also plays a big role in communication among organisms.

Bad Air? – It's hard for humans to breath Pandora's atmosphere, they must wear filtering apparatus. But the moon must be rich in oxygen from all the photosynthetic vegetation. According to the film guide a pungent mixture of hydrogen sulfide and chlorine contaminates Pandora's atmosphere. Perhaps this comes from continuous volcanism. The tidal pull from the gas giant mother planet and its other satellites must tidally pump the interior of Pandora, warming it up. As on Jupiter's moon Io, there could be continuous volcanic activity. This would keep pumping greenhouse gasses into the atmosphere, further warming the moon.

Magic Rocks – The much sought after imaginary element nicknamed "unobtanium," which is central to the storyline, is pretty farfetched (the quest for exotic elements is a common theme in a number of other science fiction stories). Unobtanium is described as a metallic superconducting crystal with the capability of powering starships and fulfilling Earth's energy needs. (And a dessert topping

and a floor wax too?)

The reality is that the universe is collectively made up of exactly the same bricks and mortar found in the periodic table of the chemical elements. We spectroscopically see these elements forged in stellar

nucleosynthesis in all corners of space. Something like unobtanium would have been cooked-up in supernovae and scattered across the galaxy.

Even if such a crystal existed - perhaps only forged under tremendous pressures deep inside a super-Earth - it would not be extractable. Even if it was, the chemistry would be easier to synthesize on Earth rather than building an interstellar Exxon Valdez to haul it between stars. Freight costs alone would kill any possibility of this material being commercially viable.

Finally, our scientists would always have the upper hand in such a discovery simply because Pandorans don't vote for Congressmen. A moon like this would be just an astrobiology curiosity. No private corporation would have the resources to mount an interstellar gold rush. What's more, corporations would be restricted by the Outer Space Treaty that explicitly forbids any government from claiming a celestial resource.

Floating Mountains – There are floating, superconducting magnetic mountains made of chunks of unobtanium on Pandora. On such a moon you might expect to find a huge electrical current inside a cylinder of a highly concentrated magnetic flux that is connected to the parent planet. Such a flux tube flowing between Jupiter and Io has the power output of about 2 trillion watts. But I'd stay clear of a field supposedly strong enough to lift a mountain. Living cells can be destroyed by extremely intense magnetic fields. The moon would have incredibly spectacular aurorae every night due to the magnetic field the moon must have to shield it from the intense radiation from the gas giant's magnetosphere. [This appears in the film, as some readers have pointed out, but I apparently missed it -- blinded by all the bioluminescence!]

"Do You Interface?" – The moon Pandora is the Gaia hypothesis gone wild. All living organisms - both animal and vegetable - intercommunicate. This Garden of Eden symbiosis seems inspired by the children's book series "Dinotopia." The Pandoran life forms even have a biological "plug ‘n play" capability. It's not clear how this would be an evolutionary advantage. It could just make dating complicated: "I've got a headache tonight dear, let's just interface."

Smurfs on Steroids – Given the infinite pathways evolution offers, it is very unlikely that 10-foot high blue humanoids would evolve elsewhere in the universe. You'd have to invoke a common origin such as panspermia from a mother super-race that seeded the galaxy with similar DNA. But clearly you can't show much of a love story between two blue blobs.

These science shortcomings aside; Avatar is still a powerfully engaging and memorable film. It's a long-awaited break from much less imaginative and silly story lines in most contemporary sci-fi films.

Artwork credit: Kees Veenenbos, Jon Spencer